Efficient Analysis of Reflectarrays through the Use of Characteristic Modes

The aim of this study is to establish an efficient analysis method for reflectarrays with varying element sizes. The efficiency of the method relies on utilization of characteristic modes as macro basis functions, and thereby reducing the MoM matrix equation size dramatically. Although the reflectarrays on the focus of this study are comprised of differently sized elements, it was observed that, when same numerical characteristic mode is used to represent the current on all patches, the resultant approximate current is sufficiently accurate to calculate the far field of the array.


Development of a pressure-based solver for both incompressible and compressible flows
Denk, Kerem; Sert, Cüneyt; Department of Mechanical Engineering (2007)
The aim of this study is to develop a two-dimensional pressure-based Navier-Stokes solver for incompressible/compressible flows. Main variables are Cartesian velocity components, pressure and temperature while density is linked to pressure via equation of state. Modified SIMPLE algorithm is used to achieve pressure-velocity coupling. Finite Volume discretisation is performed on non-orthogonal and boundary-fitted grids. Collocated variable arrangement is preferred because of its advantage on staggered arrang...
A comparison of orthogonal cutting data from experiments with three different finite element models
Bil, H; Kilic, SE; Tekkaya, AE (Elsevier BV, 2004-07-01)
The aim of this study is to compare various simulation models of orthogonal cutting process with each other as well as with the results of various experiments. Commercial implicit finite element codes MSC.Marc, Deform2D and the explicit code Thirdwave AdvantEdge have been used. In simulations, a rigid tool is advanced incrementally into the deformable workpiece which is remeshed whenever needed. In simulations with MSC.Marc and Thirdwave AdvantEdge, there is no separation criterion defined since chip format...
Simulating stochastic differential equations using Ito-Taylor schemes
Baylan, Ekin; Yolcu Okur, Yeliz; Uğur, Ömür; Department of Financial Mathematics (2014)
The aim of this work is to understand the stochastic Taylor schemes and to measure the accuracy of them by comparing their closeness to the exact solutions at the discretization points. Our assumption is that when we use the stochastic Taylor schemes with higher orders, we obtain better approximation processes to exact solutions of the stochastic differential equations. We give the stochastic Taylor schemes with different orders by regarding the convergence criteria for the stochastic differential equations...
Limitations of three-phase Buckley-Leverett theory
Akın, Serhat (Informa UK Limited, 2005-07-01)
The broad objective of this study is to determine the limitations of the three-phase relative permeability estimation technique by using the experimental approach. In order to achieve this goal, three-phase relative permeability experiments were conducted on a Berea sandstone core plug by using brine, hexane and nitrogen gas. An unsteady-state analytical technique and a numerical technique where a black oil simulator was coupled with a global optimization algorithm in a least squares manner was used to comp...
Convergence Error and Higher-Order Sensitivity Estimations
Eyi, Sinan (2012-10-01)
The aim of this study is to improve the accuracy of the finite-difference sensitivities of differential equations solved by iterative methods. New methods are proposed to estimate the convergence error and higher-order sensitivities. The convergence error estimation method is based on the eigenvalue analysis of linear systems, but it can also be used for nonlinear systems. The higher-order sensitivities are calculated by differentiating the approximately constructed differential equation with respect to the...
Citation Formats
E. Ercil, L. Alatan, and H. Ö. Aydın Çivi, “Efficient Analysis of Reflectarrays through the Use of Characteristic Modes,” 2015, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/54511.